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01-18-2025, 08:57 PM
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#1
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Senior Member
Join Date: Jul 2023
Location: Clinton, SC
Posts: 117
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Energy audit and solar project…
Energy audit and solar project…
This started with a failed propane fridge yesterday and now working toward installing a 120vac Magic Chef in our 1994 Fleetwood Jamboree E350.
From what I can tell on the web...
https://www.rvforum.net/threads/residential-rv-refrigerators.146631/page-2
The Magic Chef will draw about 75ah per day once it gets started. I'll round that up to 100ah to include losses, overhead and for ease of calculating.
I very roughly followed this guy's method to come up with the below.
https://passionhighway.com/the-complete-beginners-guide-to-rv-solar-sizing-design-installation/
See other loads below (I went high on most everything):
As for the water heater, I do not believe the spark and control is very much, maybe 1ah/day (wild guess).
Those come to an additional 244ah/day.
Rounding all that up to 400ah/day. I'll be using 4x100ah batteries. (I'll probably add another 4 later on this year).
The plans are to charge the batteries by a 20a DC-DC converter while traveling, using the generator when needed to top them off and just learning how this solar system will work for us before becoming more dependent on it.
Using 4 x 200w panels 2x2 series/parallel to charge the batteries, a 48v 30a MPPT and a 4000w inverter (available to run a microwave or toaster oven for 10 minutes a day for convenience if energy is available).
40ft of 6awg from panels to MPPT. 10ft of 1awg from batteries to inverter.
Basically I did some really rough calculations, found some charts and pulled numbers right out of the air.
I'm not going to do a transfer switch, I'll just add a couple of outlets and run a 15ft heavy duty 12awg drop cord where needed for the little bit that will be needed (microwave…).
I want to start looking for equipment that will work as above or make changes to the above to suit the equipment.
What am I missing or need to reconsider?
Thanks, Phil
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01-19-2025, 05:19 AM
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#2
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Senior Member
Join Date: Jul 2023
Location: Clinton, SC
Posts: 117
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Wow! I was wrong and still am, but headed in a better direction.
https://diysolarforum.com/ewr-carta/audit/
So you can't upload a spreadsheet?
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01-19-2025, 05:57 AM
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#3
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Community Administrator
Tiffin Owners Club
Join Date: Sep 2013
Location: DFW, Texas
Posts: 24,198
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Quote:
Originally Posted by RVers29325
So you can't upload a spreadsheet?
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No, but you can output a PDF and upload that.
__________________
2017 Phaeton 40IH XSH Maroon Coral - Power Glide Chassis with IFS
Previous '15 Tiffin Allegro RED 38QRA and '06 Itasca Sunrise 35A
White '24 Jeep JLU Wrangler Willys
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01-19-2025, 08:49 AM
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#4
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Member
Join Date: Mar 2006
Posts: 34
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Residential Fridges are awesome and you will LOVE it.
What are you planning to use for the new inverter? Are you just upgrading the existing converter to support LFP?
Side note, don't buy (4) 100ah batteries and wire them together, buy the largest AH battery that you can fit in the space instead.
It's fewer connections, 1 BMS vs 4 to monitor and much less likely to give you balancing issues down the road. Make certain whatever battery you buy has Bluetooth communications at a minimum so you can see what the battery sees. It will save you tons of time down the road when you are working on the system.
It's much easier to manage (1) 460ah or 560 ah battery than (4) 100ah and you can always add another one if you need additional capacity later rather than being maxed out at (4) 100ah, since most small BMS's can only connect up to 4x.
Reconsider that transfer switch, you need something to do the neutral/ground bonding and keeping that in the transfer switch will cut down on potential issues, especially since you have that generator. A good transfer switch will also monitor the shore power and disconnect if it is faulty, which can protect the entire coach.
Your spreadsheet doesn't include any of the typical losses from power conversion so I'd include a 10% factor for inverter waste and charging waste.
Finally, go with the largest battery cables you can to/from the pack and make sure you understand the placement and type of fuses you need for LFP packs. Regular fuses will not be suited to the instant amperage available on LFP.
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01-19-2025, 09:05 AM
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#5
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Senior Member
Join Date: Jul 2023
Location: Clinton, SC
Posts: 117
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Quote:
Originally Posted by jberger
don't buy (4) 100ah batteries and wire them together, buy the largest AH battery that you can fit in the space instead.
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Yeah, I agree, but lose my gonads getting them in/out...
Quote:
Originally Posted by jberger
Reconsider that transfer switch, you need something to do the neutral/ground bonding and keeping that in the transfer switch will cut down on potential issues, especially since you have that generator. A good transfer switch will also monitor the shore power and disconnect if it is faulty, which can protect the entire coach.
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Hmmmm, I was already thinking about a manual transfer switch for the fridge at least.
And look at this monster, I'd have to sell the house and go full time to cover the cost...
This is by far, far, far the most expensive hobby I've ever undertaken, glad she's onboard with this instead of watching me have fun and her staying home.
Thanks for the input!
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01-19-2025, 09:07 AM
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#6
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Senior Member
Join Date: Jul 2023
Location: Clinton, SC
Posts: 117
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BTW, over on the astronomy forum, I've tagged my signature with:
"I don't have a clue what I'm doing, but I'm having fun doing it"
Same here!
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01-19-2025, 09:25 AM
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#7
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Senior Member
Winnebago Owners Club Workhorse Chassis Owner
Join Date: Nov 2018
Posts: 2,999
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Quote:
Originally Posted by RVers29325
What am I missing or need to reconsider?
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Clouds and shade. Renders the most well crafted solar system moot.
Mark B.
Albuquerque, NM
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01-19-2025, 10:10 AM
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#8
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Member
Join Date: Mar 2006
Posts: 34
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Quote:
Originally Posted by RVers29325
Yeah, I agree, but lose my gonads getting them in/out...
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Why take them out? Just mount them in a good spot and leave them there, they should last for decades.
Not sure if the image you attached is your plan or someone else's, but the transfer switch would sit just after shore power and switch between Shore and Genset for neutral/ground bond and inverter for inverter loads.
If you already have a converter that does 12v to 120v, then you don't need a second inverter. You can just upgrade the converter you have in place if you need more amperage or an LFP charging profile.
Maybe you are thinking of using a stand alone inverter just for the Fridge? I can see some of the wisdom in that approach, but if your current system is really old, I'd swap the converter instead and hopefully gain some reliability.
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01-19-2025, 10:12 AM
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#9
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Senior Member
Join Date: Jan 2016
Location: Albuquerque
Posts: 152
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Yeah, I agree, but lose my gonads getting them in/out...
I have 2 460ah lithiums. Yes, 85lbs each, but with handles. Only handled them once. So much less hassle.
__________________
2024 KZ Durango Gold 358RPQ, 2018 F450 Kings Ranch
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01-19-2025, 10:21 AM
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#10
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Senior Member
Join Date: Jul 2023
Location: Clinton, SC
Posts: 117
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Quote:
Originally Posted by Mark_K5LXP
Clouds and shade. Renders the most well crafted solar system moot.
Mark B.
Albuquerque, NM
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I laughed, then I went ugh!
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01-19-2025, 10:28 AM
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#11
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Senior Member
Join Date: Apr 2024
Location: WI Driftlesser
Posts: 2,547
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Your existing batteries are a sunk cost, don't design the system around those. I'd consider EG4 3000, many of those components in one package, one attractive price. Much less wiring and "configuring" than the alternatives. All it lacks is chassis charging, and a 12V charger for the chassis. For what you save on all the avoided blue boxes, you can cover the roof with surplus commercial panels, and the EG4 will handle way more solar than you'll fit. An mppt could charge the chassis for 12v loads, off solar, or with a three way switch directly off the 48v at night.
__________________
"Bringing third world electrical work to first world luxury." RV makers of Murica!
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01-19-2025, 10:38 AM
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#12
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Senior Member
Join Date: Jul 2023
Location: Clinton, SC
Posts: 117
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Quote:
Originally Posted by jberger
Not sure if the image you attached is your plan or someone else's, but the transfer switch would sit just after shore power and switch between Shore and Genset for neutral/ground bond and inverter for inverter loads.
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Yes, it's mine, my idea was to have the inverter just for the fridge and have a outlets in a convenient place. Right now I'm just throwing ideas around on how I want it done and learning why and why not along the way.
No inverter yet, and the converter is brand new and LFP. When the old one let the magic smoke out I felt I had a great opportunity to install 2x 100ah LFP. I love them thangs!
Thanks!
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01-19-2025, 10:41 AM
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#13
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Senior Member
Join Date: Jul 2023
Location: Clinton, SC
Posts: 117
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EG4 3000... I'll check it out.
Thanks!
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01-19-2025, 11:01 AM
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#14
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Senior Member
Join Date: Nov 2018
Location: Beaver Dam, Wisconsin
Posts: 5,896
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It looks like you are going for a total off grid experience. Inverter powers the whole house. Solar recharges the batteries.
This is what I just bought in an Airstream Trade Wind.
800+ amp hours of Battle Born lithium batteries.
Victron System - MPPT Solar Controller
- 600 watts of roof solar panels
- Communication and control hub
- Multiplus II inverter/charger
Shore power feeds a 30 amp main breaker (no on-board generator)
Main breaker feeds Multiplus II
Multiplus feeds main circuit breaker panel
Multiplus manages shore power, battery charging, and inverting.
Multiplus inverter will assist shore power when using 15 amp shore outlet.
Solar charges batteries independent of other 12 volt functions. It has its own 12 volt disconnect.
Control Hub coordinates and controls all systems and displays all power flow. - Solar
- Shore Power
- Battery charging
- Load 120 volt Power
- Load 12 volt Power
This is close to the gold standard. You can do it for less money, but this would be a model to try to emulate.
Some inverters are more efficient than others. The compressor refrigerator needs constant 120 volt power? Inverter will be "ON" day and night and constantly drawing power. Get one the uses less to keep itself working.
A better refrigerator would have its own possibly built in inverter and run from 12 volts. There would be less power draw to run the small inverter. The main inverter could be shut down during the night or when RV is not occupied.
The refrigerator circuit does not need a transfer switch. The power is low enough that the main charger or solar charger can efficiently replace the 12 volt power used.
The Multiplus "assist" function can be replaced with a transfer switch to switch between inverting and shore power. Most large inverter/chargers have built in transfer switches and manage battery charging, switching, and chassis ground requirements.
You can build your own inverter charger system using components, but it must include a transfer switch. It may be a manual transfer switch or an automatic transfer switch.
Inverting mode requires a switched chassis ground connection and the charger be disconnected.
__________________
Paul Bristol
Kodiak Cub 176RD
Nissan Pathfinder 2015
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